1. Field of the Invention
The present invention relates to filter elements used to remove particulate matter from fluid streams. Specifically, the present invention is concerned with the provision of rigidized and densified fiber filters which do not require cages, rings or other fabric support hardware.
2. Description of the Prior Art
The use of filter elements made from fibers to remove particulate matter from gaseous streams is well known in the art. For example, fabric filter elements have long been deployed in bag houses, so-called because the fabric filter elements deployed therein are bag-shaped, adjacent to smoke or exhaust stacks in coal-burning electric power generating stations, to remove ash and other particulates from the exhaust gas stream before the stream as a whole exits from the stack.
It follows, of course, that periodically the filter elements must be cleaned to restore their permeabilities to some optimum value, as the particulate matter being filtered tends to accumulate on the upstream surface of a filter element, typically the outer surface of a bag-shaped configuration, reducing its permeability and the ability of the entire filter apparatus to handle the gas flow. This might be accomplished by shaking or otherwise agitating the apparatus holding the filter elements, and allowing the particulate matter to settle down on a tray or other receptacle beneath the apparatus for disposal.
Alternatively, pulses of air from a source at high pressure may be directed through the filter elements, in a direction opposite to that in which the gaseous stream being filtered normally proceeds, to dislodge the accumulated particulate matter from the filtering surfaces of the elements.
While it is necessary to clean the filter elements periodically to restore their permeabilities to desired levels, the cleaning operation itself contributes to premature fabric failure. This is often a consequence of the means used to mount the bag-shaped filter elements. Such means include cages, rings and other fabric support hardware, all usually made of metal. These rigid structures eventually cause the filter elements being flexed in a cleaning cycle to abrade and tear, producing holes requiring replacement of the filter element as a whole.
Cartridge filters are increasingly being used for industrial filtration. Cartridge filters are constructed from metal components which comprise end caps and a supporting frame and fabric or paper which forms the filter media. The number of components used in the construction and difficulty in breaking apart or compressing the elements make disposal of them difficult. The need for metal components also increases the weight of the cartridge, making handling and installation more difficult.
Accordingly, the provision of a rigidized fiber filter element, that is self-supporting and therefore does not require supporting hardware, would represent a significant advance to this field of technology. Such a fiber filter element would carry the added benefits of being readily and easily replaceable by those of a different size, in terms of length or cross-sectional area or shape, so that the filter area may be changed.
Filter elements being constructed of one material may be disposed of more easily. Lack of a supporting frame simplifies the breaking apart and compressing of the element for disposal. The element consisting solely of one material may be suitable for recycling or incineration as a means of disposal.